Learning categories composed of varying instances: The effect of classification, inference, and structural alignment

The members of a natural category are not usually identical in their appear ance, although at some level they can be described as having features in co mmon. For example, birds have wings, but the actual appearance of their win gs varies from one bird to another. To examine the effect of this feature v ariation on category acquisition, subjects in three experiments were asked to learn categories in which individual features were depicted with several different instances. The results of the experiments indicated that subject s had significant difficulty learning these categories when they were given a standard classification learning task. In contrast, subjects were able t o acquire the same categories when they were given an inference learning ta sk, in which they learned the categories by predicting a missing feature of a stimulus given the category label and information about the other featur es. Finally, subjects who were allowed to compare stimuli during learning w ere able to learn the categories. These results suggest that a common descr iption of different instances emerges in the process of aligning stimuli.